Wolli Birds

Tuesday, September 2, 2008

The Bird's Nest is a resource for primary school teachers about birds in the Wolli Creek Valley and surrounding areas. It features laminated A3 coloured posters with teachers notes on the reverse. The posters have accompanying worksheets for students. The resource also contains a Powerpoint presentation on urban birds and the birds of the Wolli Valley.

The Bird's Nest is not designed for use online. The following is a preview of the contents to help you plan your study of Wolli birds. Read through the table of contents below (much of which links to image previews) or scroll down to see the thumbnails at the end.

Saturday, July 26, 2008

A night fauna survey was conducted by DECC in 2007. Owls calls were played out into the Valley but no replies were heard.

Since this, however, a number of species have been observed in the Valley. The Tawny Frogmouths (not technically an owl) were the first.

On 11 April 2008 a school group paused near Wave Rock and discovered a Southern Boobook right in front of them! After excited whisperings, pointings and a few discreet photos the group moved away to discuss the importance of the find.

Even more significant was the sighting by Gavin Gatenby on 29 May 2008 of a Powerful Owl near in Girrahween Park. It was thought this species might turn up. A camp of Grey-headed flying-foxes had arrived in Wolli and been growing in numbers since June 2007. The Powerful Owl is one of the bats' few natural predators.

Tuesday, February 5, 2008

On the evening of 5 August 2007, Gavin Gatenby spotted what he thought was a male Variegated Fairy Wren and his troop in thick scrub near the escarpments on the Girrahween track. He reports "Luckily I had my camera with me and, braving the low-light conditions, I took a quick shot, resulting in a lousy image, but good enough to confirm the first ever sighting of the species in the Wolli Valley".

A chance conversation in Turrella Reserve, with photographer Alexander Choi, unearthed photos he'd taken of this species and excitement reached an all time high when Voren O'Brien discovered two adult males, a female and a nest of young Variegated Fairy Wrens on her nature rounds before the WCPS Committee Xmas dinner in 2007. Photos were quickly developed and circulated at the restaurant!

To an inexperienced observer the Variegated Fairy Wren (Malurus lamberti) might understandably be mistaken for the well-known “Blue Wren” (officially known as Superb Blue Wren) but it’s difficult to see how its presence could have escaped the notice of such an experienced birdwatcher as the late Neil Rankin who meticulously recorded the valley’s birdlife until his death in 2001. These are not the sort of birds that can suddenly migrate into the area from many kilometers away, so we can only conclude that a small remnant population has been present, all along, in the nearby Bardwell Valley, from which they have now recolonised Wolli.

Here the female carries food to her young. The nestlings are concealed in a domed, grass nest with a side entrance very close to the ground.

A sad postscript to this story is the discovery, the very next day, that the nest was empty apart from some large black ants. It's impossible to say what predator is to blame. Snakes are major nest predators of Fairy Wrens and large birds such as Currawongs will take eggs or nestlings of smaller birds. And perhaps it is no coincidence that only two weeks earlier a fox was spotted mere meters from this very nest.

But the species seems to be fairly resilient. A family group has been spotted on the Girrahween Track near Cormorants Corner and while the female will not reuse her original nest it ishoped that she will build elsewhere and attempt a second brood.

Postscript: In July 2008 a male Variegated Wren was observed in Jackson's Quarry.

Tuesday, August 7, 2007

Tawny frogmouths, an owl-like night bird have been rediscovered in the Wolli Valley, after an absence of at least 38 years. A pair of the cryptic pigeon-sized birds has recently taken up residence in Girrahween Park where they were spotted by sharp-eyed Voren O’Brien of the Wolli Creek Preservation Society.

“These birds are Australian icons, imitating broken grey branches to remain unseen. Seeing them in the Wolli Valley so close to Sydney’s centre is a special thrill”, Voren said. Records of bird species seen in the valley since 1940 are available in Birds of Wolli Valley, published by the Preservation Society last year. They show a single sighting of a frogmouth between 1940 and 1969 and none since. The book is based on the research, personal observations, and meticulous records of the legendary Wolli birdo, Neil Rankin, between 1970 and his death in 2001.Tawny frogmouths are relatively common in bushland around Sydney but have probably only recolonised the Wolli Valley very recently. The birds are active at night, hunting small animals such as mice, frogs and insects. By day they roost on branches close to a tree trunk where their bark-coloured plumage makes them almost invisible to an untrained observer.

Monday, August 6, 2007

An injured bird, unable to fly, is a concern to most of us. Last Wednesday (20 June) Peter Stevens of the Wolli Creek Preservation Society came across one on the Undercliffe Track in the Wolli Valley. With the help of fellow member, Judy Finlason, who lives nearby, a light towel was thrown over the bird, which was then lifted carefully into a box. Quick reference to a bird identification guide suggested that it was a native Fruit-Dove. “This made it a real rarity this far south” an excited Peter said.

On the advice of WIRES, the volunteer wildlife rescue group, the bird was taken to a local vet, in this case Peter Nicholl of the Earlwood Animal Hospital. The two Peters were able to take a few photos of the bird to aid identification before the bird was collected by local WIRES carer, Chris Lloyd, a bird specialist. The bird has a badly injured and bloodied wing, with many feathers missing and, even with antibiotics and intensive attention, it will be several months before it can be released, provided its wing recovers sufficiently.

Experienced ornithologists have agreed that this a first-year male Purple-crowned (Superb) Fruit-dove, never before reported in the Wolli Valley. Alan Leishman of the Society advises that the bird has only been recorded in the Sydney region about 20 times since 1953 and only once before that (in 1876!). “This bird would be considered to be an uncommon one in the Sydney region and the current specimen probably on migration”, Alan said. These Fruit-doves possibly occur more often than the records indicate, as they are difficult birds to see while quietly feeding among the outer foliage of berry-bearing trees, often high up. “This is such an interesting find”, Peter Stevens said. “While a cautious stance is entirely appropriate – it could be an aviary escapee after all – this may add yet another bird` to the 176 species reported in the Wolli Valley since 1940.” And it comes on top of another find – only the second reported sighting of Tawny Frogmouths in the valley since 1940. Chris Lloyd reports that, based on its behaviour, his young patient is unlikely to have been an aviary bird, but may be young enough to have still been partially dependent on its parents. “This is an even more exciting possibility”, Peter Stevens says, “since it could mean that the birds have bred in the Valley, once again underlining the major regional significance of the Wolli Valley bushland.”

Fifty hectares of the Wolli Valley, including most of its bushland is finally about to become a Regional park under the National Parks and Wildlife Service over the next few months. “We keenly hope that the Fruit-dove not only recovers, but can be released back into the Wolli bushland.” Peter Stevens concluded.

The continuing story...

Our bird expert assessed the situation as follows: "I would identify the bird in the photographs as a 1st year male Superb Fruit Dove, Ptilinopus superbus. The identification is based on the colour of iris, colour of feet and general plumage. The age is based on the general plumage, I am not able to check the shape of the outer primaries or the wing coverts or the shape of the rectrices, it would be necessary to have the bird in the hand to do this. The colour of the legs and feet are more like the adult colour that the true juvenile colour of grey-horn. The sexing is based on the colour at the base of the bill and the slight colour on the flanks of the shoulder.

Superb Fruit Doves nest between June and February (Handbook of Australasian and New Zealand Birds Vol 3) thus making this specimen at least 4 months old, probably is slightly older. The Handbook of Australian Birds states that this species commences its post juvenile moult when 70-90 days old, hence the wash of colour on the flanks of the shoulder.

As far as records for the Sydney region "The Birds of Sydney" states that:

“On 16 May 1953, an immature bird was found dead near Epping. This was the first record of the species near Sydney since 1876 when two birds were collected at ‘North Shore’. Of 17 known occurrences [up to 1989] at least eight birds were killed flying into windows. Possibly occurs more often than the records indicate as it is a difficult bird to see while quietly feeding among the outer foliage of berry-bearing trees".Two birds were recovered dead in 1992, one in Sydney and one in Wollongong. This bird would be considered to be an uncommon bird in the Sydney region and the current specimen probably on migration."Another source reports: "WIRES east branch has had 1 superb fruit-dove and 2 rose crowned fruit doves (or vice versa) in the last 18 months. They may not be as uncommon as thought."In 2002 a Superb (purple-crowned?) Fruit-dove hit a window at Twyford Avenue, Earlwood and died. Young male starting to moult. As at June 2007 it is kept frozen in The Australian Museum, College Street, Sydney.

Bird update:

The dove is fine to date and has been moved out of intensive care into a small hospital aviary. It has completed its antibiotic course but still requires two crop feeds a day. The latter indicates that it was likely to be still dependant on adults for crop milk. While it does not like human contact and has little understanding of cage wire it does seem to accept crop feeding - this may indicate captive breeding though I still doubt this. The next step for the bird is feather regrowth - it has no retricies and is missing most of the left primaries and secondaries. It will then become clear if it has full use of the carpal joint.Standard Operating Practice for WIRES with birds in this catagory is freezing and delivery to the Aust. Museum - presuming they don't make it.

An update:

"Its weight fluctuated substantially for a week until the tell-tale signs of a 50mm tapeworm appeared. Having lost this burden it is now much more active and weighs in at 88g (it came in at 80g). The left wing is currently bandaged as it consistently opened the damaged flight feather folicles and lost blood.

This bird is seriously lucky to be alive when the full extent of the injuries are totalled up. The tapeworm is interesting in that its size indicates the bird had it prior to the injuries which begs the question was the debilitation from the nematode the reason it was on the ground and therefore attacked.It still shows no inclination to self feed no matter how many Californian cherries are chopped up for its delectation. So it gets 2 crop needles a day."

The latest update from WIRES:

The Fruit Dove has maintained a stable weight at 94-98grams for the past few weeks. It has put new primary, secondary remiges out but many of these are damaged and mis-shaped. This is not unusual and often reflects folicle damage that may repair on the next molt. We will have to wait to see whether there will be sufficient feathers for flight and therefore release. If the damage to the left wing folicles is more serious it may mean plucking and another wait. If the damage is permanant then I think our patient will be surrendered to the tender mercies of Taronga. Until it has sufficient feather development for flight its a little academic.

I have sourced adult calls and will start play these into its cage though it remains relatively wild anyway. Still has a marked preference for Californian cherries unfortunately! It would be very useful if any of your members could identify native fruits in the Wolli valley that we could transition the bird on. Its wild preference is for fruit in the 5-15mm diameter particularly dark red-blue - sounds like a privet eater but could also be Port Jackson figs. Any help in this area would be greatly appreciated.

November update:

The fruit dove was moved to a larger aviary a few weeks ago and is doing well but still has some problems with the coverts and flight feathers of the left wing. These may be permanant and would prevent the normal range of movements for wild behaviour. Its is now colouring up nicely.

My partner and I moved to the Wolli Valley in 1980. In the quarter-century since, I’ve witnessed big changes in the local birdlife. A few species have disappeared locally. Although some – mostly feral – are seen less often, some species have become much more common. Some species, never, or only rarely, seen in the 1980s, have become common. A few species once present only in the remnant natural habitats of the valley have begun to move into nearby suburban gardens.

The late Neil Rankin, who compiled fifty years of bird observations in the Wolli Valley – the work of himself and others – in the 1989 edition of Birds of Wolli Creek, witnessed and recorded many of these changes before his death in 2001. Others have occurred since.

In some cases these changes are part of much wider movements seen across the Sydney Basin and down the east coast, but others probably occur for local reasons. Ecosystems are made up of infinitely complex interactions, and in urban environments all manner of human actions can have unintended impacts, for good or ill, on our non-human fellow-travellers. What follows is what I like to think of as informed speculation, based on my own observation and reading, about the reasons for these changes. I hope it will stimulate discussion and observaton.

The “island biogeography” effect

Ecologists have spent a great deal of time studying the fauna of islands, large and small, and have discovered a set of laws that govern how many species are likely to be found on an island, based on its size and relative isolation. The concept of “island biogeography” is also useful in understanding the occurrence of species in isolated fragments of native vegetation like the Wolli Valley bushland.

Think of the valley as a small island of viable habitat in a sea of suburbia, unsuitable for most native birds. Birds that are highly mobile (such as ducks), can reach this island, and survive there for some time, but it may not be big enough, or suitable enough, to sustain them for long. Even if they manage to breed, and establish a small colony, the group is vulnerable to local extinction through predation, disease or infertility. On the other hand, the amount of habitat may be sufficient to support a viable colony.

We have also to factor into the equation the fact that European settlement severely modified the original bush. Trees were cut down, some important plant species (such as cabbage-tree palm) disappeared, and cattle, goats and pigs trampled and grazed the vegetation. By the early 20th Century, Wolli was, in ecological terms, almost a desert island – completely unsuitable for many native birds that had once thrived there. But here and there, in inaccessible places, small patches of bush remained and after agriculture declined, communities of native plants began, once again, to spread over the area, re-creating lost habitat. It has taken some decades for some of the vanished species to find their way back – a process that continues.

Decline of the ferals

In my observation, the ubiquitous feral birds of the Sydney I grew up in – the House Sparrow, Starling, and Spotted Turtle-dove – have declined during the last quarter of a century.

The reasons aren’t too hard to find.All three species were highly dependent on humans for food, and the Sparrow and Starling on man-made structures for nesting places. Mostly, Sparrows and Starlings nested in the rooves of old, poorly-maintained, often weatherboard, houses. When we moved into our old cottage in Turrella, there were Sparrows or Starlings nesting in all four corners of the ceiling. Structures like these have mostly been pulled down or gentrified and the renovations have blocked entry holes, forcing these birds to nest in sub-optimum places (such as palm trees) where they’re more vulnerable to predation by Currawongs and Ravens.

The decline of poultry-keeping, cage birds and horses

In his justly celebrated song about urban wildlife ecology, quoted at the start of this essay, Fats Waller puts his big finger on the fact that technological change is an important factor in the rise and decline of avian species within our cities.

An important reason for the decline of the European House Sparrow, the Starling, and the Indian Turtle-dove has been a marked decline in the practice of keeping poultry and cage birds in suburbia. If you’ve ever kept backyard chooks, you’ll know that feral birds show great enterprise in raiding chook runs for food.

The disappearance of the few remaining horses from the Wolli Valley has eliminated another source of spilled wheat and oats – a rich source of food for feral birds. This completes a process that began when the railways, the electric tram, and finally cars, buses and trucks drove horse-drawn transport off our streets.

Urban reforestation

Another impetus to change has been the steady “reforestation” of Sydney’s suburbs. In my youth, eucalypts, wattles and casuarinas (let alone native shrubs like banksias and grevillias) weren’t a common feature of the suburban landscape. People mostly planted exotics like roses, wisteria, camellias, fuschias, non-native deciduous trees and exotic pines in their gardens.With the exception of the exotic pines (conifers), this flora is almost useless to native birds. In the case of the exotic conifersthere was, in fact, a food windfall, but the native birds hadn’t yet learned to exploit it, and it would be some decades before they did. There were plenty of big, mature, Pinus radiata near where I grew up in Strathfield, but I never saw a Yellow-tailed Black Cockatoo until decades later. Nowadays, these cockatoos are a regular visitor wherever these conifers exist.

From the 1960s on, growing affluence and the movement towards respect for our native flora encouraged more householders to plant native trees and shrubs with high value for honeyeaters, lorikeets, cockatoos and insectivores, and to create an artificial vegetation structure that mimicked their natural environment. Urban reforestation has probably also accellerated the process of recolonisation controlled by the island biogeography effect I discussed above by helping birds cross suburbia to the Wolli bushland. Gardens and small parks landscaped with natives have become stepping-stones for the recolonisation of the valley.

To illustrate how these factors (and others) have affected our native species let’s look at some individual species.

Australian Pipit

Neil Rankin rated Pipits as “very common” up to 1988, but this meant that he was seeing the same pair, in the same place, month after month. For the first years I lived in the valley this pair could almost always be seen on the open grass of Turrella Reserve near Nannygoat Hill. They disappeared many years ago and have not returned. I put this case down to island biogeography. Perhaps one or both the birds were killed by a cat or a raptor. Perhaps they died of old age. Perhaps they just decided to move to greener pastures. At the time of writing, no other pair of Pipits has recolonised this piece of habitat. There was only ever sufficient habitat for one pair of pipits. This is a very clear example of the island biogeography effect. The disappearance of that pair removed the species from the Wolli habitat “island” – a fact that will remain until another pair of Pipits happens upon the valley.

Yellow-tailed Black Cockatoo

This species had never been recorded in the valley when Rankin wrote the first edition of Birds of Wolli Creek. Their return is an exciting event and they’re now a very common visitor, with flocks of up to 25 feeding on wood-boring grubs and banksia and casuarina seeds. The Yellow-tailed Black Cockatoo has benefited from the mass planting of casuarinas over the last 30 years, from old plantings of exotic pines, and from the regeneration of banksias in the valley itself.

Superb Fairy Wren (“Blue Wren”)

Blue Wrens remain very common in the valley and can always be seen where scrubby habitat interfaces with mown grassland. Technically this sort of abrupt transition is known as an “ecotone”. Many people feel Blue Wrens declining in suburban gardens, which may be correct. In my own garden they were much bolder and more visible in the past. They still occur but are rather secretive, a fact that may reflect the increased presence of currawongs. I believe their decline might also be related to the fact that nowadays fewer households are keeping dogs. Dogs exclude cats from backyards and Blue Wrens are reluctant to nest where cats occur.

Red Wattlebird

Neil Rankin rated this bird as “uncommon” in the period 1982–88, seeing them on less than half of his transects. They are now a ubiquitous feature of the valley’s bushland (for example on the slopes of Nannygoat Hill) and are common in streets and gardens. Their rise is almost certainly related to the vastly increased food supply provided by the planting of red bottlebrushes as street trees, the popularity of grevilleas as garden plants, and the gradual regrowth of banksias in the bushland. Wattlebirds pugnaciously defend their nests against nest-robbers like currawongs. To survive on these mean streets it helps a lot to be pugnacious.

White-browed Scrub Wren

Neil Rankin rated these small wrens as “scarce”. They are now frequently encountered in the valley and in early 2005, a family of six, including two juveniles, began to visit our garden which is 400 metres from the nearest typical habitat. I have never previously seen them outside bushland or gardens on the edge of the bush. Perhaps they’ve benefited from a couple of decades of bush restoration in the valley, supplemented by nearby suburban native gardens.

Red-browed Finch

Once confined to the Wolli bushland these beautiful little native finches are now frequent visitors to gardens around the valley. In ours they spend days on the ground and the roof, under our casuarinas, looking for fallen seed, and when these run out they scour the trees, pulling the remaining seeds out of the fruits. Even outside the casuarina seed season small family parties sometimes visit in company with Australian White-Eyes (Silvereyes?) or Blue Wrens. Their rise is clearly related to increased food sources, such as casuarinas.

Brown Goshawk

In my experience the Brown Goshawk is becoming much more common. It preys on smaller birds, notably feral or domestic pigeons (rock doves), as well as mice and rats. Eucalypts planted in the 1960s and 70s are now tall enough to provide nesting opportunities. The recent proliferation of compost bins has brought with it new opportunities for the house mouse and the black rat, and may be partly responsible for the increase in this species.

Boobook Owl

After only a handful of records over a 50-year period the boobook was rediscovered by Neil Rankin in the late 1990s. They are now regularly sighted roosting during the day and heard calling at night. I have photographed one in the valley and heard them at night in our garden, where I suspect they’re hunting the mice that make a living out of our compost bin. Owls need quiet secluded places to roost during the day and sizable tree hollows in which to nest. One regularly roosts in an exotic conifer in a Bexley North garden. I think the Boobook’s return reflects the steady regrowth of woodland in the valley.

Spangled Drongo

Until 1988, Rankin rated the Drongo as scarce. Of recent years this migrant has become a seasonal fixture in suitably wooded gardens and along streets, as well as in bushland. Its rise may be due to our gradually warming climate as well as revegetation.

Sacred Ibis

Becoming more common in parks and along creek flats, the Sacred Ibis is now something of a nuisance species throughout Sydney. It has few natural predators and it has found that its long, sensitive bill, which evolved for probing for beetles, worms, and insect larvae in soft soils, is beautifully “pre-adapted” for probing in rubbish bins for discarded sandwiches.

Common Koel

The Koel is a cuckoo. Most cuckoos are parasitic – laying their eggs in the nest of another species and allowing the foster parents to raise their offspring. Koels migrate each year from New Guinea and the Lesser Sunda Islands and they parasitise Orioles, Magpie-Larks and Red Wattlebirds, all of which are present in the valley. Neil Rankin rated them as “scarce”, and they were certainly not a regular feature of the valley when I first moved here. They are now an inescapable feature of spring and summer, even if most folk only hear their persistent call. Adult Koels mostly eat native figs, supplies of which are increasing, but the rise in Koel numbers is probably due to the increased number of Red Wattlebirds whose nests can be parasitised.

Channel-billed Cuckoo

People who worry (in my opinion excessively) about the depradations wrought on the small native bird population by Currawongs can take heart from the relentless rise of this very large parasitic cuckoo. Until about 2001 they were almost never seen in the Wolli Valley and none were recorded by Neil Rankin or earlier observers.

During the winter, Channel-bills migrate south from New Guinea arriving here in the spring. They mostly parasitise Currawongs, but at first, those reaching the valley were a few weeks too late to parasitise the Currawongs’ first breeding attempt (Currawongs often try for two broods in a season). The Channel-bills now strike with unerring accuracy. Since the 2003 season, the Currawongs that nest in our garden have raised at least three Channel-bill chicks and only a couple of their own. As this phenomena reproduces itself across Sydney, the failure to recruit to their own population will certainly bring about a collapse in Currawong numbers.

The downside is that living with a growing Channel-bill is a great deal more stressful for humans than living with baby Currawongs. They’re incredibly noisy and persistent and they stay with their hapless foster parents a lot longer than Currawongs.

Topknot Pigeons

With the regrowth of the Wolli bushland and the planting of more native trees in local gardens, the Topknot Pigeon has been seen more often in the valley and in larger numbers. Neil Rankin’s only records were of 7 birds in 1984 and 15 in November 1986. These big, grey, rainforest pigeons with their floppy brown topknot are using the valley as a welcome migration route through the hostile Sydney landscape. I have seen about 40 feeding on soft green Angophora fruits, but the valley also provides magenta lillipilli fruit. Once, I found a dead, emaciated, juvenile Topknot in my front garden. The Cabbage Tree Palms recently found regenerating in the Wolli Creek and Bardwell valleys may be from seeds carried in by rainforest pigeons like the Topknot.

Crested Pigeons

Neil Rankin first observed one of these charming native pigeons in 1982 but they’re now very common. They feed extensively on the tiny seeds of native figs and casuarinas, a resource not favoured by the introduced Spotted Turtle-dove, which is declining in numbers as the supply of human waste and domesticated bird food diminishes.

Rainbow Lorikeet

“In the main, birds overfly the valley”, Rankin noted of the Rainbow Lorikeet, and rated them as uncommon. Rainbow Lorikeets are one of those species that, in retrospect, can be seen as excellently pre-adapted to the mean streets of the big city – provided only that a sufficient supply of abundantly pollen- or fig-bearing native trees are on hand. The species is pugnacious, intelligent, very social, and unafraid of humans and can rapidly travel long distances to exploit a temporary food supply. Consequently, numbers have increased spectacularly throughout Sydney. There’s now a breeding colony in the palms lining Mawson Street, Turrella. The local increase of this bird simply reflects a much wider trend.